I did a search on the local drive and see the file.

This error has been published in Sage 500 knowledgebase ID:36976. Here are the step to resolve it:

Reinstall Sage 500 ERP client using Local Administrator account (Windows Built-In Administrator).

When removing current Sage 500 ERP client installation, make sure all the files are removed including the Registry files. (For further information, please refer to the related article link below )

Also from Start, use the Search programs and files to look for the presence of the appconfig.dll file.

Depending on the system being 32 bit or 64 bit, you may need to move the appconfig.dll from C:windows\System32 into the C:windows\Syswow64 folder, unregister the version in system32 folder and register appconfig.dll in the syswow64 folder.

In one case, with the installation of a 7.4 Sage 500 client, .NET 4.5 needed to be uninstalled and .NET 4.0 needed to be installed before the Sage 500 client could be installed.

Thanks for the help. That worked!